If you have an account on LinkedIn, you can check if your password was leaked/cracked - http://shiflett.org/blog/2012/jun/leakedin
If you haven't changed your password yet, I'd recommend changing it before checking to see if it's on the list. I trust the site link above - Chris Shiflett is a well-known and trusted PHP developer and blogger on security issues.
How do we respond to this, as a community-focused system? There are 3 parts to all of this - authentication, authorization, and cryptography - and we need to address them all.Authentication:
encrypting, hashing and hiding sensitive data for transmission and storage
Logging into a website uses all 3.
@madfish has explained some of the principles of this in the documentation for the Yubikey module - the basics of authentication are in knowing or having something unique. 1-factor authentication only requires one or the other. 2-factor authentication requires both.
The sites that were recently hacked failed because they had poor cryptography. 2-factor authentication would have reduced their risk dramatically, as would better general programming.
In all of this, we have not talked about policy - another major factor in the security of any system. Recommended read - http://www.schneier.com/blog/archives/2010/11/changing_passwo.html
It talks mostly about password rotation, but covers some good points about having passwords appropriate for the content they protect.